Drive control mechanism for motor vehicles and detent device therefor



Max 'ch 2, 1948. A. w. BONHAM, JR

DRIVE CONTROL MECHANISI FOR HOTOR VEHICLES AND- DE'1ENT DEVICE THEREFOR Filed Dec 8, 1945 5 Sheets-Sheet 1 March 2, 194 8. w, BQNHAM, JR 7 7 2,436,912

DRIVE CONTROL MECHANISM FOR MOTOR VEHICLES AND DETENT DEVICE THEREFOR Filed Dec. a, 1945 5 Sheets-Sheet 2 Ame/Mm I moi/Wm March 2, 1948. A. w. BONHAM, JR 6,

DRIVE CONTROL MECHANISM FOR MOTOR VEHICLES AND DETENT DEVICE THEREFOR Filed Dec. 8, 1945 5 Sheets-Sheet s March'Z, 1948. A. w. BONHAM, J R

DRIVE CONTROL MECHANISM FOR MOTOR VEHICLES AND DETENT DEVICE THEREFOR Filed Dec; 8., 1945 5 Sheets-Sheet 4 'DRIVE CONTROL MECHANISM FOR MOTOR VEHICLES AND DETENT DEVICE THEREFOR Filed Dec. 8, 1945 5 sheets-sheet 5 Patented Mar. 2, 1948 I 2,4sa912 narva oon'raor. MECHANISM roa MOTOR VEHICLES AND DETENT DEVICE THERE- FOR Albert W. Bonham, In, Salt Lake City, Utah, as- I liner to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Dela- Application December 8 1945, Serial No. 833,811

12 Claims.

The invention relates to motor vehicles, and it is concerned more specifically with an improved mechanism for controlling the operation of such vehicles, more particularly as to starting and stopping thereof. 1

In tractors which are steered by driving, that is, in which steering is effected by varying the drive of ground engaging traction devices at opposite sides of the vehicle, it is usual to provide a pair of clutches, commonly referred to as steering clutches, for controlling the drive of the traction devices. In such tractors, a pair of control levers, one for each steering clutch, are suitably mounted within reach from an operator's seat, and by properly manipulating these control levers, the operator may drive the tractor either straight ahead, or to the right or left, and .he may also interrupt the drive of both traction devices by adjusting the control levers to neutral positions, as is well-known in the art.

In addition to the steering clutches in such tractors, two sets of reverse mechanisms are sometimes employed, one for each traction device, the purpose of such reverse mechanisms being to permit driving of the traction devices in opposite directions forshort turning, and to permit simultaneous reverse drive of both traction devices, if desired.

U. 8. Letters Patent No. 2,197,248, dated April 16, 1940, and granted to A. W. Bonham, Jr.', and A. B. Bonham, for Tractor, discloses two such sets of reverse mechanisms in combination with a pair of steering clutches, and it also discloses a pair of control levers, one for each traction device, which are so interrelated with the steering clutches and reverse mechanisms, that the tractor will have the following operating characteristics. First, when bothcontrol levers are in neutral positions, no power will be transmitted to the traction devices while the vehicle motor is running and the change speed transmission is in gear; in other words, adjustment of the two control levers to their neutral positions causes demobilization of the vehicle. Second, when the control lever for the right hand traction device is adjusted forwardly from its neutral position, while the tractor motor is running and the change speed transmission is in gear, power from the motor is transmitted to the riEht hand traction device to drive' the latter forwardly; and when the right hand control lever is adjusted rearwardly from its neutral position the right hand traction device is driven reversely. That is,- adjustment of the right hand control lever from its neutral position in either direction causes mobilization of the vehicle. "lhird, when the control lever for the left hand traction device is adjusted forwardly from its neutral position while the tractor motor is running and the change speed transmission is in gear, the left hand traction device is driven forwardly; and when the left hand control lever is adjusted rearwardly from its neutral position, the left hand traction device is driven reversely. That is, adjustment of the left hand control lever from its'neutral position in either direction causes mobilization of the vehicle, and in this respect, the left hand lever functions in analogy to the right hand control lever.

An important requirement for a tractor which is operable in the herelnabove outlined manner is the provision oi.suitable detent mechanisms for releasably retaining the control levers in their neutral positions. Obviously, it is desirable that the control levers should stay in their neutral positions after they have been adjusted to said positions in order to demobilize the vehicle, because it would otherwise be impracticalmr the operator to leave the demobilized vehicle without first stopping the motor or at least putting the change speed transmission out of gear. In connection with such detent mechanisms it is highly important for practical reasons, as will appear hereinbelow, that they function to safely secure the control levers against accidental release after they have been adjusted to their neutral positions in order to demobilize the vehicle.

Generally, it is an object of the present invention to provide an improved motor vehicle having' two control members and power transmitting means operative in response to adjustment of either of said control members tomobilize and demobilize the vehicle.

More specifically, it is an object of this invention to provide in a motor vehicle having steering clutches and reverse mechanisms of the general character outlined hereinbefore, an improved dual control mechanism including two control levers and detent mechanisms therefor, which will safeguard the vehicle against accidental mobilizatioh due to unintentional release of one or both detent mechanisms. I p

A further object of this invention is to provide a dual control mechanism of the above outlined character, and in which the control levers have a tendency to adjust themselves automatically to to first adjust both control levers in opposition to their tendency to move into drive-establishing positions,'before either one can be moved from its neutral into a drive-establishing position.

A further object of the invention is to provide I a motor vehicle having a dualcontrol mechanism as outlined hereinbefoz'e, and in which resilient means are provided to urge the control levers towards drive-establishing positions, and the detent mechanisms for the control levers are so arranged and function in such a manner that initial movement of the control levers from their the character outlined hereinbefore, which is simple and compact in construction, efficient in operation, and which may be manufactured at relatively low costs.

The foregoing and other objects and advantages of the invention will become more fully apparentfrom the following description of a preferred embodiment of the invention shown in the accompanying drawings. Referring to the drawings in which like reference characters designate the same or similar parts in the several views:

Fig. 1 is a side view of a four wheel drive tractor;

Fig. 2 is a top view of the tractor shown in Fig. 1;

Fig. 3 is an enlarged rear view of power transmitting and control mechanisms incorporated in the tractor shown in Figs. 1 and 2, housing parts of the tractor being shown in section substantially along line III-III of Fig. 1;

Fig. 4 is a detail view of strut appearing in Fig. 3;

Fig. 5 is a diagram of a steering clutch and reversing mechanism shown in Fig. 3;

Fig. 6 is a side view of the control mechanism and of parts of the power transmitting mechanism shown in Fig. 3, the view of Fig. 6 being taken substantially on line VI-VI of Fig. 3;

Fig. 7 is a perspective view of a latch element appearing in Figs. 3 and 6;

Fig. 8 is a top view of a cam and actuating member appearing in Figs. 3 and6;

Figs. 9 to 13 are diagrams illustrating different positions of adjustment of the control mecha-' nism shown in Figs. 3 and 6.

Referring to Figs. 1 and 2, the tractor shown in these figures is of the type in which steering is effected by varying the drive of ground engaging traction devices at its opposite sides. A pair of rubber tired tandem wheels I and 2 are mounted, at the left side of the tractor, on a casing 3 for rotation about fixed axles 4 and 6, respectively, and another pair of rubber tired tandem wheels I and 8 (Fig. 2) are mounted, at the right side of the tractor, on a casing 9 for rotation about fixed axles in alignment, respectively, with the axles 4 and 6. A body housing II between the casings 3 and 9 comprises a spation of the housing II, the latter being of genverse rear portion of the housing II, each of the casings 3 and 9 having a central flange intermemediate its front and rear ends, and the housing II being suitably flanged at the opposite ends of its transverse rear portion for connection with the central flanges, respectively, of the casings 3 and 9. The forwardly extending portions of the casings 3 and 9 on which the wheels I and I, respectively, are mounted are laterally spaced from the longitudinal forwardly extending portion of the housing II, the latter terminating at its forward end in a vertical flange I2. Rigidly connected with the housing I I at the flange I2 the cylinder block of an internal combustion engine I3, the engine or motor I3 being of conventional construction and serving to furnish propelling power of the tractor.

The motor I3, the housing II and the casings 3 and 9 form the body structure of the tractor, which is sustained on the wheels I, 2, l and. 8. Suitably mounted on said body structure are a radiator and radiator shell I4, a hood I6, a fuel tank I'I, an operator's seat I8, a pair of fenders I9, and a power take-oil: unit 2 I The forward portion of the body housing II, immediately behind the motor I3 encloses a conventional master clutch associated with the flywheel (not shown) of the motor I3, afoot pedal for controlling the master clutch being indicated at 22 in Fig. 1. A conventional change speed transmission (not shown) which is controlled by a gear shift lever 23 is enclosed in the longitudinal portion of the body housing II which extends forwardly from the rear transverse portion of the latter. A cross shaft 24 (Fig. 3) which is rotatably mounted in the rear transverse portion of the body housing II carries a bevel gear 26 which permanently meshes with a bevel pinion 21 on the output shaft of the change speed transmission. The mechanism through which power is transmitted from the motor I3 to the cross shaft 24, and which comprises the mentioned master clutch and change speed transmission, conforms as to its construction and arrangement with ordinary automotive practice. When the motor I3 is running, transmission of power to the shaft 24 may be effected in the usual manner by first disengaging the master clutch, then placing the change speed transmission into any selected gear, and then gradually engaging the master clutch. In other words, when the motor I3 is running, the shaft 24 will be rotated about its axis as long as the master clutch is engaged and the change speed transmission is in gear.

Referring to Figs. 1 and 3, a sprocket shaft 28 is rotatably mounted in the casing 3 at the left side of the tractor in axial alignment with the cross shaft 24, and a similar sprocket shaft 29 is rotatably mounted in the casing 9 and in axial alignment with the cross shaft 24, at the right side of the tractor. The sprocket shaft 28 has integrally formed therewith two sprocket pinions 3| and 32, which are connected in driving relation, respectively, with the wheels I and 2, as indicated in Fig. 1. A roller chain 33 within the casing 3 is trained over the sprocket pinion 3I and over a sprocket pinion 34 which is geared within the housing 3 to the axle 4 of the wheel I. Another roller chain 36 within the casing 3 is trained over the sprocket pinion 32 and over a sprocket pinion 31 which is geared within the casing 3 to the axle 6 of the wheel 2. The wheels 1 and 8 at the right side of the tractor are connected in driven relation with the sprocket shaft 28 in the same manner as explained hereinbefore in connection with the wheels I and 2 and the sprocket shaft 28. two sprocket pinions 38 and 38 being integrally formed with the shaft 28, as shown in Fig. 3.

Referring to Figs. 3 and 5, a steering clutch and reversing mechanism is operatively interposed between the cross shaft 24 and the sprocket shaft 28, and a similar steering clutch and reversing mechanism is operatively interposed between the cross shaft 24 and the sprocket shaft 28. As shown diagrammatically in Fig. 5, the steering clutch and reversing mechanism between the cross shaft 24 and the sprocket shaft 28 comprises a planet carrier 4| which is rotatable relative to the cross shaft 24; a sun gear 42 and a driving clutch member 43 which are connected with the cross shaft 24 for rotation in unison therewith: a composite driven member 44 which posite driven member 44 through the clutch disks I 48, and a clutch shifter yoke 5| (Fig. 3)-is mounted within the housing for disengaging said driving connection. The shifter yoke 5| is swingable back and forth in the general direction of the axis of shaft 24 about a pivot center 58 on the housing l, and the shifter yoke 5| is so arranged that the loading springs 48 tend to swing said yoke about the pivot center 80 in the direction of arrow A in Fig. 3, and so thatswinging movement of the yoke 5| about the pivot center 80 in the direction of arrow B in Fig. 3 disengages the steering clutch comprising the clutch disks 46.

The composite driven member 44 (Fig. 5) includes a ring gear 52 which is internally geared to the planet plnions 41, and the latter, in turn, are permanently geared to the sun gear 42. The brake band 48 is wrapped around a drum portion 83 of the planet carrier 4|, as more clearly shown in Fig. 6, one end of the brake band being anchored on the housing and its other end being connected with a mechanism for tightening and loosening the brake band, to which mechanism further reference will be made hereinbelow.

The steering clutch and reversing mechanism which, as stated hereinbefore and as shown in- Fig, 3, is operatively interposed between the cross shaft 24 and the sprocket shaft 29 at the right side of the tractor, is an opposite hand duplicate of the steering clutch and reversing mechanism which is interposed at the left side of the tractor, between the cross shaft 24 and the sprocket shaft 28, and the foregoing explanations with respect to the left steering clutch and reverse mechanism similarly apply to the right steering clutch and reverse mechanism. Like the steering clutch comprising the clutch disks 48, at the left side of the tractor, the steering clutch at the right side of the tractor is engageable and ing ii at 88. Swinging movement of the shifter yoke 84 about the pivot center 88 in the direction of arrow A in Fig. 1 causes engagement of the right steering clutch, and swinging movement of the yoke 84 in the opposite direction indicated means of a mechanism which is substantially a duplicate of the tightening mechanism for the brake band 48.

In connection with the cross shaft 24 it has been stated hereinbefore that said shaft is being rotated when the tractor motor i8 is running and the change speed transmission in the forward part of the housing is in gear. The clutch shifteryokes 8| and 84 are shown in Fig. 3 in clutch disengaged positions, and accordingly, no power will be transmitted from the shaft 24 to the sprocket shafts 28 and 28' through the left and right steering clutches, while the shaft 24 is rotating and the shifter yokes 8| and 84 are positioned as shown in Fig. 3. The planet carriers 4| and 88 are rotatable relative to the shaft 24, and if the brake bands 48 and 88 are loose while the shaft 24 is rotating and both steering clutches are disengaged, the reverse mechanisms represented by the planetary gearings at the right and left of the tractor will likewise be ineffective to transmit power from the shaft 24 to the sprocket shafts 28 and 28. That is, the ring gear 82 which is part of the composite driven member 44 at the left side of the tractor will remain stationary, and the planet carrier 4| at the 'clutchesare disengaged and both brake bands are loose.

The direction in which the shaft 24 rotates when the crank shaft of the motor i3 rotates in its predetermined direction and when the change speed transmission is in one of its forward drive gears is indicated in Fig. 3 by the arrow C. Assuming now that, while both brake bands 48 and 88 are loose, and while the shaft 24 rotates in the direction of arrow 0 the left steering clutch is engaged by swinging movement of the shifter yoke 8| in the direction of arrow A. As a result of such engagement of the left steering clutch the drive wheels I and 2 will be driven in a forward direction. Similarly, the drive wheels I and 8 may be driven by swinging movement of the shifter yoke 84 in the direction of arrow A and consequent engagement of the right steering clutch. For normal forward drive of the tractor both steering clutches are engaged, while both I brake bands 48 and 88 are released so as not to impede rotation of the planet carriers 4| and 88, the latter rotating in unison with the shaft 24 and with the composite driven members 44 and 81 when the steering clutches are engaged.

Assuming next that while the shaft 24 is rotating in the direction of arrow C and while both steering clutches are disengaged, the brake band 48 is tightened upon the brake drum 53 of the planet carrier 4|. As a result of such tightening of the left brake band 48 the drive wheels I and 2 will again be driven but in reverse direction because the composite driven member 44 will now be driven by the shaft 24 through the sun gear 42,

the planet pinions 41 and ring gear 52. Similarly,

the drive wheels I and B of the tractor may be driven in reverse direction by tightening the brake 'band 59 upon the brake drum of the planet carrier 58 while the steering clutch at the right side of the tractor is disengaged.

The shifter yoke 5| and the brake band 48 are operatively connected with a manually operable control lever 6| (Fig. l) which is pivotally mounted on the housing I and has a handle end at convenient height, at the left side of the tractor, within reach from the operators seat l8; and the shifter yoke 54 and the brake band 58 are operatively connected with a similarcontrol lever 62 (Figs. 2 and 3) which has a handle end at the right side of the tractor, and which is an opposite hand duplicate of the control lever 6|.

As shown in Figs. 3 and 6, a rock shaft 63 is rotatably mounted in an upper part of the housing I, and an inner end portion of the rock shaft 63 projects into a pocket 64 formed in the top wall of the housing II. The control lever 6| is nonrotatably secured on the projecting end portion of the rock shaft 63 within the pocket 64, as by means of a set screw 66.

Non-rotatably secured to the rock shaft 63 within the housing H is a cam and actuating member 61 which is shown in side elevation in Fig. 6, and a top view of which is shown in Fig. 8. As

portion of the strut section 18 adjacent to the shifter yoke BI is machined down and terminates shown in Fig. 3, the member 61 is mounted on an intermediate portion of the rock shaft 63, and it is secured on said rock shaft against rotation relative thereto by a set screw 68. Extending radially from and integrally formed with the hub of member 61 at the side of the latter next to the pocket 64 is a cam portion 69 provided at its periphery with a dovetail recess 1 i, and with cylindrical cam surfaces at the peripherally opposite sides of the recess 1 I, the cam surfaces extending in a common cylindrical plane coaxial with the rock shaft 63. Formed at the side of the cam portion 69 remote from the pocket 64, and integral with hub of the member 61 is a clutch actuating arm 12 which extends radially beyond the cam portion 69, and which has at its outer end a spherical socket 13. Also integrally formed with the hub of the member 61, and at the end of said hub remote from the pocket 64 is a brake actuating arm '14 to which one end of the brake band 48 is connected by means of a pin I6, as best shown in Fig. 6.

Referring to Fig. 4, a strut generally indicated by the reference character 11, is operatively interposed between the clutch actuating arm 12 of the member 61 and the upper end of the shifter yoke 5| for the left steering clutch. The strut ll is made in two sections 18 and 19 which are threadedly connected together as shown at 8|, the strut section 18 having a tapped axial bore in a relatively longhexagonal portion thereof, and the strut section 19 having a threaded shank portion which is screwed in to the tapped bore of the strut/section 18. The threaded connection between the strut sections 18, I9 permits adjuststrut has been adjusted to its desired length. The

in a ball head which is seated in a spherical socket formed at the upper end of the shifter yoke 5|. The portion of the strut section 18 adjacent to the arm 12 of the member 61 has a ball head which is seated in the spherical socket 13 (Fig. 8) of the arm I2.

The shifter yoke 5| is shown in Fig. 3 in clutch disengaged position, as has been stated hereinbefore, and While in said position it is subject to thrust, by the loading springs 49 of the left steering clutch, in the direction of arrow A in Fig. 3. Said thrust upon the shifter yoke 5| is transmitted through the strut 'I'I to the member 61 which in turn is rigidly mounted, as stated, on the rock shaft 63. Fig. 6 shows the member 61 adjusted to an angular position about the axis of rock shaft 63, in which the center of the spherical socket l3 coincides with a horizontal plane through the axis of the rock shaft 63, and the strut Tl in the assembled mechanism is adjusted to such a length that when the member 61 is adjusted to the position shown in Fig. 6, the shifter yoke 5| will occupy the position in which it is shown in Fig. 3, that is, a clutch disengaged position. The brake band 48 is so arranged that when the member 61 is adjusted to the angular position in which it is shown in Fig. 6, the brake band will be slack, that is, substantially inoperative to produce a braking effect upon the planet carrier 4|.

The control lever 6| is non-rotatably secured to the rock shaft 63, as stated hereinbefore, and Fig. 6 shows the angular position which is occupied by the lever 6| when the member 61 occupies the position in which it is shown in Fig. 6, and in which position of the member 61 the left steering clutch is disengaged and the brake band 48 is slack, as has been explained hereinbefore. Upon movement of, the lever 6| from the position in which it is shown in Fig. 6, in the direction of arrow 1 in said figure, and which arrow denotes forward swinging movement of the lever 6| relative to the tractor, the ball head of the strut section 19 moves on an are about the axis of the rock shaft 63 while the ball head of'the strut section I8 moves on an are about the pivot center 52 of the shifter yoke 51 and in a vertical plane through the common axis of shafts 24 and 28. The movement to which the ball head of the strut section 18 becomes subjected as a result of forward swinging movement of the control lever 6| from the position in which said lever is shown in Fig. 6, is in the direction of arrow A in Fig. 3, and it will therefore be seen that such forward swinging movement of the lever 6| causes engagement of the left steering clutch.

Upon movement of the control lever 6| from the position in which it is shown in Fig. 6, in the direction of arrow 1 in said figure, and which arrow denotes rearward swinging movement of the lever 6| relative to the tractor, the ball head of the strut section 19 again moves on an are about the axis of the rock shaft 63 while the ball head of the strut section 18 moves on an are about the pivot center 50 of the shifter yoke 5| and in a vertical plane through the common axis of the shafts 24 and 28. However, the movement to which the ball head of the strut section 18 becomes subjected as a result of rearward swinging movement of the control lever 6| from the position in which said lever is shown in Fig. 6, is in the direction of arrow B in Fig. 3, and the left steering clutch will therefore remain disengaged when the control lever 6| is swung rear- 'wardly from the position in which it is shown position in which it is shown in Fig. 6 in order I to engage the left steering clutch, and that rearward swinging movement of the control lever 8| from the position in which it is shown in Fig. 8 will cause tightening of the brake band 48 upon the brake drum 88 while the left steering clutch remains disengaged;

Referring again to Fig. 3, the rock shaft 88 is rotatably mounted at its outer end in a wall portion 88 of the housing II by means of a ball bearing 84. A portion of the rock shaft 88 between the wall portion 88 and the hub of the cam and actuating member 81 is surrounded by a coiled torsion spring 88 which is anchored at one end thereof on the housing wall 88, and the other end of the spring 88 is anchored on the hub portion of the cam and actuating member 81. The coil spring 88 is so arranged that it will be wound up or torsionally tensioned by movement of the control lever 8| in the direction of arrow 1' in Fig. 8, and the spring is installed.

during assembly of the mechanism, in asultably wound up condition so that it will have a permanent tendency to move the control lever 8| from its clutch disengaged or neutral position which is indicated in Figs. 1 and 8 by the dashdotted line N1 to its extreme forward position which is indicated by the dash-dotted line F in Fig. 1, and which extreme forward position corresponds to full engagement of the left steering clutch. In the condition of the mechanism as shown in Fig. 6, the control lever M is prevented from moving from its position Nrtowards the position F by a releasable latch devicewhich will be described hereinbelow, and when the latch device is released the torque of the coil spring 88 shaft 83, is mounted on the'housing II at the right side of the pocket 84 and in axial alignment with the rock shaft 88. The control lever 82 is non-rotatably secured to the rock shaft 81 within the; pocket 88, and a cam and actuating member 88, which is an opposite hand duplicate of the cam and actuating member 81, and has a cam portion 88 (Fig. 3), is a non-rotatably secured to the rock shaft '81 within the housin II. A strut 88, which is a. duplicate of the strut I1, is operatlvely interposed between the member 88 and the shifter yoke 84, and the brake band 58 is connected with a forwardly extending brake actuating arm of the member 88 in the same manner as illustrated in Fig. 6 with respect to member 81 and thebrake band 48. A coiled torsion spring 8| corresponding to the torsion spring 88 reacts between the housing II and the member 88, and tends to move the control lever 82 into its extreme forward position which corresponds to full engagement of the right steering clutch.

Referring to As pointed out hereinbefore' in connection. with Fig. 3, the rock shaft as whichca'rries the/control lever 8| and thecam and actuatingmember 81, j and the rock shaft 81 which carries the"control.

lever 82 and the cam and actuating member 88;

are rotatably mounted on the housing II in axial alignment with each other, and the dash-dotted'f line Xin Figs. 9 to-13; therefore, represents the commo'n axis of the rock shafts 88 and 81. These rock shafts are rotatable on the housing I I' about the common axis X independently of each other,

and Fig. 8 shows the control lever 8| and the member 81 in a position corresponding to that in which these parts are shown in Fig. 6, that is in the neutral position N1. The control lever 82 and member 88 areshown in Fig. 9 in a position of adjustment corresponding to the neutral position Ni. of the control lever 8| and member 8,], that is, in a neutral position. which is indicated in Fig. 9 by the reference character N1.

The control levers 8| and 82 are releasably secured against forward swinging movement from their neutral positions N1 and Ni, respectively, in

which they are shown in Fig. 8, by a latch device which also limits rearward swinging movement of the levers 8|, 82, independently of each other, from their neutral positions N1 and N1; and said latch device is constructed as follows.

Referring to Figs. 3, 6 and '7, a three-armed 'latch element shown in detail in Fig '7 and genpocket 84, and it projects into the housing II at the left and right sides, respectively, of said pocket. As best shown in Fig. 6. the axis of the latch shaft 88 is located rearwardly of and somewhat below the axis of the rock shaft 88, and the double-armed lever 84, 88 is non-rotatably secured to the shaft 88, as by a set screw I88. The top wall of the housing II has an opening 88, and the actuating arm 88 of the latch element 82 extends upwardly throughthe housing opening 88. A dished cover 88 is mounted on the housing II over the aperture 88 and a thrust rod I8I which is pivotally connected to the upper end of the actuating arm 88 extends forwardly from the latter and through an opening in the front wall of the cover 88, the rod |8| being slidably supported in the opening'of the cover for back and forth movement relative thereto. A coiled compression spring I82 surrounding the rod I8I within the cover88 is seated at one end on the front wall of the cover 88, and it bears, at its other end L against a washer I88 which is backed by a cross pin I88 mounted on the rod I8I.' In the posi- Fiss- 8 to 18, each of these figures shows the cam and actuating members 81 and 88- diagrammatically and insuch relation to each other as to perspectively indicate the 'rnounting of the members 81 and-88 one, common axis which is represented by the dash-dotted line 1! arm 96 through the washer I 88, pin I 94 and rod IOI.

Referring to Fig. 3, the trigger arm .91 of the latch element 92 is non-rotatably secured to the latch shaft 98 within the housing II at the right side of the pocket 64, as by means of another set screw I88. It .will also be noted from Fig. 3, that the relative transverse spacing of the trigger arms 94 and 91 matches the relative transverse spacing of the cam portions 69 and 89 of the cam and actuating members 61 and 88. or in other words, the free end of the trigger arm 94 registers with the cam portion 69 of the member 61, and the free end of the trigger arm 91 registers with the cam portion 89 of the member I38 as shown in Fig. 3. For purposes of illustration, the transverse width of the free end of the trigger arm 94 is shown in Fig. 3 as being slightly shorter than the transverse width of the cylindrical cam surfaces of the cam portion 69, and the free end of the trigger arm 91 is shown as being slightly shorter than the transverse width of the cam portion 89.

Referring to Figs. 9 to 13, the cam portion 89 of the cam and actuating member 88 has a dovetail recess I86 corresponding to the dovetail recess II of the cam portion 69. The dash-dotted line Y in Figs. 9 to 13 represents the axis of the latch shaft 93, and the trigger arms 94 and 91 are secured to said shaft in such positions that their free ends engage the dovetail recesses II and I06, respectively, when the control levers 6| and 62 are in their neutral positions N1 and N1. respectively, as shown in Fig. 9. As shown in Figs. 7 and 13, the trigger arm 94 terminates at its free end in a foot piece the toe portion of which has a slanting surface I81, and the heel portion of which terminates in a shoulder I88 at right angles to the sole of the foot piece. As shown in Fig. 13, the dovetail recess II has a bottom surface I69 and converging sides III and I I2, the side III providing an undercut portion on the cam 69 for cooperation with the slanting surface I91 of the foot piece of the trigger arm 94, as shown in Fig. 9. The side III of the recess II terminates in a sharp edge H3 at the cylindrical periphery of the cam portion 69, and the side I I2 0! the recess 7| terminates in a blunt, rounded edge 4 at the cylindrical periphery of the cam portion 69. The circumferential spacing between the edges 3 and N4 of the recess II is somewhat larger than the spacing between the toe edge H9 (Fig. 13). and the shoulder 18 of the foot piece at the free end of the trigger arm 94.

The surface I9! is formed on the trigger arm 94 at such an angle that when the foot piece of said trigger arm projects into the recess H, and

the control lever 6| is in the neutral position N1,"

as shown in Fig. 9, the side Iii of the recess II bears flatly upon the surface I81. Said surface contact between the cam portion 69 and the trigger arm 94 secures the control lever 6| against forward swinging movement from the position N1 in which it is shown in Fig, 9, It should further be noted, particularly with reference to Figs. 6 and 9, that when the control lever 6| is in its neutral position N1, in which it is shown in said figures, the latch element 92 cannot be rotated about the axis of the latch shaft 93 in either direction. The trigger arm 94 has an abutment II1 (Fig. 13) which bears upon the cylindrical surface of the cam 69 adjacent to the blunt edge 4 of the recess II when the parts are positioned as shown in Figs. 6 and 9, and the thrust of the spring I02 which tends to swing the latch element 92 about the axis of shaft 98 in one direction is taken up by the contact of the abutment III with the cam 69. On the other hand, swinging movement of the latch element 92 about the axis of shaft 98 in the opposite direction is positively prevented, while the parts are positioned as shown in Fig. 9, by the engagement of the slanting side III of the cam 89 with the slanting surface I01 of the trigger arm 94, the slant of the side III being such as to make it impossible for the foot piece of the trigger arm 94 to swing out of the recess H while the control lever 6| is in its neutral position N1.

However, it will be noted that when the parts are positioned as shown in Fig. 9, the blunt edge 4 of the recess 'II is spaced circumferentially from the radial shoulder I98 of the trigger arm 94, and the'control lever 6| may therefore be moved rearwardly from the neutral position N1 until the blunt edge 4 of the recess II engages the shoulder I08 of the trigger arm 94. This condition is shown in Fig. 11, and the corresponding position of the control lever 6| is indicated in said figure by the reference character N2. When the lever 6| is in the position N2 the side wall III of the recess H no longer impedes swinging movement of the foot piece of the trigger arm 94 out of the recess II, and reference to the actual release of the foot piece from the recess II will be made more fully hereinbelow.

The trigger arm 91 of the latch element 92, has

a foot piece at its free end which is a duplicate of the foot piece at the free end of the trigger arm 94. Accordingly, the same reference numerals which are applied in Figs. 7 and 13 at the foot piece of the trigger arm 94 are applied, in the same figures, at the foot piece of the trigger arm 91. The cam and actuating member 88 which is connected with the control lever 62 through the rock shaft 81' is an opposite hand duplicate of the cam and actuating member 61 and, accordingly, the same reference numerals which are applied in Fig. 13 to the various elements of the recess II are applied, in the same figure, to the corresponding elements of the recess I96.

The explanations given hereinbefore with reference to the relations which exist between the trigger arm 94 and the cam portion 69 when the control lever 6| is in its neutral position N1, as shown in Fig. 9, similarly apply to the relations which exist between the trigger arm 91 and the cam portion 89 when the control lever 62 is in its neutral position N1, as shown in Fig. 9. That is, when the parts are positioned as shown in Fig.

9, the foot piece of the trigger arm 91 coacts with the recess I86 to positively prevent forward swinging movement of the control lever 62 from its neutral position N1, and to positively lock the latch element 92 against swinging movement about the axis of shaft 93 in either direction. The latch element 92 is thus, in efiect, double locked against swinging movement about the axis of shaft 93 in either direction when the parts are positioned as shown in Fig. 9, rotation of the latch element 92 in one direction being prevented by contact of the abutment III on the trigger arm 94 with the cylindrical cam surface of the member 69, and by contact of the abutment II! on the trigger arm 91 with the cylindrical cam surface of the member 89; and rotation of the latch element 92 in the opposite direction being prevented by engagement of the side III of the recess 'II with the surface I91 on the foot piece of the trigger arm 94, and by engagement of the When the control lever BI is in its neutral position N1 as shown in Figs. 1. 6 and 9, and the con-.

trol lever 82 is in its corresponding neutral position N1, as shown in Fig. 9. both clutch shifter yokes i and 54 (Fig. 3) are in clutch disengaged positions and both brake bands 48 and 59 are slack, that is, practically ineffective to produce a. braking effect upon the planet carriers 4I and 68. Assumingthat the tractor motor I3 is running and that the gear shift lever 23 is in a forward drive establishing position, the cross shaft 24 (Fig. 3) will be rotated, but no drive will be transmitted either to the drive wheels I and 2 or to the drive wheels 'I and 8, as long as the control levers 8i and 82 are in their neutral po'sitions N1 and N1, respectively. Nor will a drive be estabfrom its neutral position N1, to its neutral position N2.

As indicated in Fig. l, the angle a through which the control lever Si is movable between the positions Ni and N2 is relatively small, and the range of movement of the control lever 8| denoted by the angle a constitutes an idling range of the control lever GI. The control lever 82 has a corresponding idling range, the same as indicated by the angle a in Fig. i.

After the operator has climbed on the seat I8 he takes hold of the handle ends of both levers 6| and 82 and pulls them rearwardly from their neutral positions N1 and Ni, respectively, into the neutral positions N2 and N2, respectively. Such rearward movement of the control levers 8i and 82 establishes the condition illustrated in Fig. 11. That is, the sides III of the recesses 'II and I08 no longer impede swinging movement of the foot pieces of the trigger arms 94 and 91 out of the recesses II and I08, respectively, and while the latch element 92 is locked against swinging movement as long as the control levers BI and 82 are in their neutral positions N1 and N1, respectively, the latch element 92 becomes unlocked by movement of both control levers 8i and 62 into their neutral positions N2 and N2, respectively. It will be noted, however, that when the control levers 8I and 82 are in their neutral positions N2 and N2, respectively, as shown in Fig. 11, the foot pieces of the trigger arms 94 and 91 still project into the recess 'II and I08, respectively, and the latch element 92, under the conditions illustrated in .Fig. 11, may be defined as being unlocked for movement into a released position.

Inorder to move the latch element 92 into released position with respect to the members 61,

88, the operator may pull both control levers 6|,

82 rearwardly beyond their idling ranges, 01' he may pull only one of the control levers rearwardly beyond its idling range. while he maintains thev other control lever at the rear limit of its idling range. Fig. 12 illustrates the. condition which obtains when the operator pull the control lever 82 rearwardlybeyond its idling range while he maintains the control lever 8I in its neutral position Nz.' As shown in Fig. 11, the blunt edge I I4 of the recess I00 bears upon the shoulder I08 of the trigger arm 91, and when the operator pulls the lever 82 rearwardly beyond the position N2, while the lever Si is maintained in its position N2. the rearward pull on the lever 82 is transmitted-to the latch element 92 through the blunt edge II4 of the reces I08 and the shoulder I08 oi the trigger arm 91. with the result that the latch element 92 will be forced to rotate about the axis of the shaft 93 in opposition to'the pressure of the spring I02. Such rotation of the latch element 92 causes it to move into the released position which is illustrated in Fig. 12. Instead of forcing the latch element 92 into the mentioned released position by pulling the control lever 82 rearwardly beyond its position N2, the operator may accomplish the same result by pulling the control lever 8| rearwardly beyond its position N2 while he maintains the control lever 82 in its position N2; or he may pull both control levers simultaneously to the rear beyond their positions Ni! and Na, respectively.

After the operator has unlocked the latch element 92 in the manner described hereinbefore (Fig. 11). and after he has then released it according to any one of the aforementioned methods (Fig. 12), the operator may let-the control levers 8| and 82 swing forwardl into their forward drive establishing positions corresponding to the dash-dotted line F in Fig. 1. In doing so. however, he will have to let the levers follow each other in suitable sequence so as to prevent the foot pieces of the triggerarms 94 and 91 from re-entering the recesses II and I08,-respeev tively. This is illustrated in Fig. 13, wherein the foot piece of the trigger arm 94 is shown as bearing' upon one of the cylindrical cam surfaces of the cam portion 89, and wherein the foot piece of the trigger arm 81 is shown 'as bearing upon one of the cylindrical cam surfaces of thecam portion 89. Obviously. the lever 62 can be swung from the latch releasing position in which it is shown in Fig, 13, into the forward drive establishing position represented by the dash-dotted line F in Fig. 1, without impediment by the trigger arm 97, because the latch element 92 is maintained in released position, against the action of the spring I02, due to contact of the trigger arm 94 with the cylindrical surface of the cam portion 89.

Steering of the tractor to the right may be accomplished by movement of the control lever 82 from the position F in Fig. 1 to the position 'R in said figure, while the control lever 0| is left in the position F, and steering of the tractor to the left may be accomplished by movement of the lever 6| to the position R while the control lever 82 is' left in the position F, From the explanations given hereinbefore in connection with Fig. 13, it will be seen that manipulation of the control levers 8i and 82 in the stated manner is not impeded by the latch element 92.

The operator may also adjust both control levers iii, 82 to the position R in Fig. 1, while the.

swing the control levers into their positions N1 and N1, and as a result, the latch element 92 becomes double locked, as explained hereinbefore in connection with Fig. 9.

The fact that the latch element 92 is double locked, as stated. when the control levers GI and 62 are in their neutral positions N1 and N1, is an important safety feature of the control mechanism. For instance, the operator may desire to leave the tractor after he has stopped it by adjusting the control levers 6|, 62 to their neutral positions N1 and N1, respectively, and while the motor I3 is running and the gear shift lever 23 is left in a drive establishing position. In dismounting from the tractor, under these conditions, the operator may take hold of the control lever at the side of the tractor at which he is dismounting, and while relying on said lever for support he may pull said lever to the rear. If he is dismounting at the right side of the tractor, the lever subject to rearward pull would be the lever 62, and Fig. illustrates the condition of the control mechanism under the assumed circumstances. That is, the control lever 62 is shown in Fig. 10 as being pulled into its position N2, while the control lever 6| i shown in its position N1 into which it is urged by the loading springs 49 of the leftsteering clutch and by the spring 86. Rearward pull on the lever 62, in the position of the parts as shown in Fig. 10, will be transmitted to the latch element 92 through the blunt edge II I of the recess I06 and through the shoulder I08 of the trigger arm 91, and the latch element will therefore tend to swing about the axis of the shaft 93 in opposition to the pressure of the spring I02, However, the latch element 92 cannot yield to this tendency of swinging about the axis of shaft 93 in th mentioned direction because it is still locked against rotation in said direction by engagement of the side III of the recess II with the surface I01 of the trigger arm 94. Therefore, the tractor cannot be mobilized by rearward pul'ron the lever 62 while the lever 6| is in its position N1, and when the operator 7 in dismounting from the tractor, or in climbing upon the tractor, should desire to rely on the control lever 62 for support, he may safely doso without danger of accident although the motor I3 may be running and the change speed transmission be in gear.

While in the foregoing explanations it has been assumed that the operator pulls on the lever 62 while the lever 6| is in its neutral position N1, it is equally safe for the operator to pull on the lever 6| when he dismounts from the tractor or climbs into the seat, while the tractor motor is running and the change speed transmission is in gear, provided that the control lever 62 is in its neutral position N1. In that case the latch element 92 is locked by cooperation of the foot piece of the trigger arm 91 with the recess I06, and the tractor cannot be mobilized accidently by rearward pull on the control lever 6 I.

The cam portions 69 and 89, and the latch element 92 with its two trigger arms 94 and 91 pro- 16 vide a pair of releasable detent mechanisms which are operative to determine primary limit positionsN1 and N1 and secondary limit positions N2 and N2 of the control levers 6| and 62, respectively. Further, the detent mechanisms include locking means, namely, the sides III of the recesses II and I06, and the surfaces I01 of the trigger arms 94 and 91, which are operative to lock said detent mechanisms as long as one of the control levers 6|, 62 is in its aforesaid primary limit position, and to unlock said detent mechanisms, as illustrated in Fig. 11, upon adjustment of both of said control levers into their secondary limit positions N2 and N2, respectively. Adjustment of the control levers 6| and 62 beyond their secondary limit positions N2 and Nz','respectively, is yieldingly opposed by the detent mechanisms after the latter have been unlocked, as has been explained hereinbefore in connection with Figs. 11 and 1-2. The blunt edges II4 of the recesses "II and I06, and the shoulders I08 of the trigger arms 94 and 9! constitute actuating means for the latch element 92 which are operable to release the latch element upon adjustment of both control levers to their secondary limit positions N2 and N2, and upon subsequent adjustment of one said control levers beyond its secondary limit position. The cylindrical cam surfaces of the cam members 69 and 89 constitute check means cooperable with the latch element 92 so as to maintain the latter released as long as either of the control levers 6 I, 62 is in a position of adjustment beyond either limit of its idling range,

The latch element 92, the check means 69, 89, the control levers GI, 62 and the torsion springs 86, 9| are functionally interrelated so that either torsion spring will be effective to urge its associated control lever into the extreme forward position whenever the latch element is maintained released by operation of the check means associated with the other control lever, and so that both torsion springs will be precluded from moving the control levers into their extreme forward positions when both check means have been rendered inoperative to maintain the latch element released. That is, whenever the latch element 92 is maintained released by operation of the check means associatedswith one of the control levers, the other control lever may assume its extreme forward position F under the action of its associated torsion spring, or it may be adjusted manually in opposition to said spring action, to any other desired position, and when the feet of the trigger arms 94, 91 have snapped into the dovetail recesses II and I06, respectively, or in other words, when the check means 69, 89 have been rendered inoperative to maintain the latch element 92 released, the control levers BI and 62 are precluded from moving under the action of the torsion springs 86 and 9| into their extreme forward positions F due to engagement of the locking means represented'by the sides I II of the recesses II and I06 with the surfaces I01 of the trigger arms 94 and 91, respectively.

It should be understood that it is not intended to limit the invention to the exact details of construction herein shown and described for various claims may occur to persons skilled in the art.

It is claimed and desired to secure by Letters.

Patent:

traction devices and operative to drive one or the other of said traction devices'in response to adjustment of one or the other of said control members, respectively, beyond said idling range, and a pair of releasable detent mechanisms associated, v

respectively, with said control members and operative to determine primary and secondary limit positions of each of said control members within said idling range, said detent mechanisms including locking means operative to lock said detent mechanisms as long as one of said control members is in its said primary limit position and to unlock said detent mechanisms upon adjustment of both of said control members to their said secondary limit positions.

'2. In a motor vehicle, in combination, two conv of releasable detent mechanisms associated, re-

spectively, with said control members and operative to determine primary and secondary limit adjustment of said control members beyond their said secondary limit positions, locking means operative to lock said latch means as long as one of said control members is in its said primary limit position, and actuating means for' said latch means operable to release the latter upon adjustment of both of said control members to their said secondary limit positions and upon subsequent adjustment of one of said control members beyond its said secondary limit position.

5. In a motor vehicle, in combination, two control members adjustable independently of each other within a predetermined idling range, power transmitting means adapted to drive a pair of traction devices and operative to drive one or the other of said traction devices in response to adjustment of one or the other of said control members, respectively, beyond said idling range, a pair of detent mechanisms associated, respectively,

positions ofeach of said control members within 4 said idling range, said detent mechanisms including locking means operative to lock said detent mechanisms as long as either of said control members is in its said primary limit position and to unlock said detent mechanisms upon adjust; ment of both of said control members to their secondary limit positions; and means resiliently urging said control members towards their said primary limit positions.

3. In a motor vehicle, in combination, two control members adjustable independently of each other within a redetermined idling range, power transmitting means adapted to drive a pair of traction devices and operative to drive one or the other of said traction, devices in response to adjustment of one or the other of said control members, respectively, beyond said idling range, a pair of detent mechanisms associated, respectively, with said control members and operative to determine primary and secondary limit positions of each or said control members within said idling range, said detent mechanisms including latch means operable to releasably secure said control members against movement beyond their said primary limit positions and to yieldingly oppose adjustment of said control members beyond their said secondary limit positions, and locking means operative to lock said latch means as long as one of said control members is in its said primary limit position and to unlock said latch means upon adjustment of both of said control membersto their said secondary limit positions.

4. In a. motor vehicle, in combination, two control members adjustable independently of each other within a predetermined idling range, power transmitting means adapted to drive a pair of traction devices and operative to drive one or the other of said traction devices in response to adjustmentof one or the other of said control members, respectively, beyond said idling range, a pair of detent mechanisms associated, respectively, with said control members and operative to determine primary and secondary limit positions of each of said control members within said idling range, said detent mechanisms including latch means operable to releasably secure said control members against movement beyond their said primary limit positions and to yieldingly oppose with said control members and operative to determine primary and secondary limit positions of each of said control members within said idling range, said detent mechanisms including common latch means operable to releasably secure said control members against movement beyond their said primary limit positions and to yieldingly oppose adjustment of said control members beyond their said secondary limit positions, looking means cooperable with said latch means to lock the latter as long as one of said control members is (adjusted to its said primary limit position, and actuating means for said latch means operable to release the latter upon adjustment of both of said control members to their said secondary limit positions and upon subsequent adjustment of either of said control members beyond its said secondary limit positions; and check means associated with said control members and cooperable with said latch means to maintain the latter released as long as either of said control members .is in a position of adjustment beyond either of its said limit positions.

6. In a motor vehicle, in combination, two control members adjustable independently of each other within a predetermined idling range, power transmitting means adapted to drive a pair of traction devices and operative to drive one or the other of said traction devices in response to adjustment of one or the other of said control members, respectively, beyond said idling range, a pair of releasable detent mechanisms associated, respectively, with said control members and operative to determine a primary limit position of each of saidcontrol members at one end of said idling range, and a secondary limit position of each of said control members at the other end of said idling range, said detent mechanism including locking means operative to lock said detent mechanisms as long as either of said control members is in its said primary limit position and to unlock said detent mechanisms upon adjustment of both of ,said control members to their said secondary limit positions;

'7. In a motor vehicle, in combination, two control members adjustable independently of each other within a predetermined idling range, power transmitting means adapted to drive a pair of traction devices and operative to drive one or the other of said traction devices in response to adjustment of one or the other of said control mem bers, respectively, beyond said idling range, a pair of releasable detent mechanisms associated, re-

spectively, with said control members and operative to determine a primary limit position of each of said control members at one end of said idling common latch means operable to releasably secure said control members against movement beyond their said primary limit positions and to yieldingly oppose adjustment oi. said control members beyond their said secondary limit positions, locking means cooperable with said latch means to lock the latter as long as either or said control members is adjusted to its said primary limit position, and actuating means for said latch means operable to release the latter upon adjustment of both or said control members to their said secondary limit positions and upon subsequent adjustment of either 01' said control members beyond its said secondary limit position; and check means associated with said control members and cooperable with said latch means to maintain the latter released as long as either of said control members is in a position oi adjustment beyond its said primary limit position.

8. In a motor vehicle, in combination, two control members adjustable independently of each other within a predetermined idling range, power transmitting means adapted to drive a pair of traction devices and operative to drive one or the other of said traction devices in response to adjustment of one or the other or said control members, respectively, beyond said idling range, a pair of releasable detent mechanisms associated, respectively, with said control members and operative to determine a primary limit position of each of said control members at one end of said idling range, and a secondary limit position oi each oi said control members at the other end of said idling range, said detent mechanisms including common latch means operable to releasably secure said control members against movement beyond their said primary limit positions and to yieldingly oppose adjustment of said control members beyond their said secondary limit positions, locking means cooperable with said latch means to preventrelease 01 the latter as long as either of said control members is adjusted to its said primary limit position, and actuating means for said latch means operable to release the latter upon adjustment of both of said control members to their said secondary limit positions and upon subsequent adjustment of either of said. control members beyond its said secondary limit position; primary check means associated with said 20 latch element, in said operative position of the latter, to positively prevent movement of said control members in one direction beyond primary limit positions, respectively, within said idling.

I direction to secondary limit positions within said idling range and upon subsequent movement of either of said control elements in said opposite direction beyond its saidsecondary limit position,

control members and cooperable with said latch means to maintain the latter released as long as either of said control members is in a position of adjustment beyond its said primary limit position, and secondary check means associated with said control members and cooperable with said latch means to maintain the latter released as long as either of said control members is in a position of adjustment beyond its said secondary limit position.

9. In a motor vehicle, in combination, two control members adjustable independently of each other within a predetermined idling range, power transmitting means adapted to drive a pair of traction devices and operative to drive one or the other of said traction devices in response to adjustment of one or the other of said control members, respectively, beyond said idling range, a support adjustably mounting said control members, a latch element resiliently movable on said support from an operative to a released position, abutment means associated, respectively, with said control members and cooperable with said said abutment means and said latch element having relatively interlockable portions for securing said latch element against movement from said operative to. said released position as long as either of said control elements is in it's said primary limit position. 7

'10. In a motor vehicle, in combination, two control members adjustable independently of each other within a predetermined idling range, power transmitting means adapted to drive a pair of traction devices and operative to drive one or the other of said traction devices in response to adjustment of one or the other of said control members, respectively, beyond said idling range, a support adjustably mounting said control members, a latch element resiliently movable on said support from an operative .to a released position, primary abutment means associated, respectively, with said control members and cooperable with said latch element, in said operative position of the latter, to determine primary limit positions of said control members, respectively, within said idling range, and secondary abutment means associated, respectively, with said control members and cooperable with said latch element, in said operative position of the latter to determine secondary limit positions, respectively, of said control members within said idling range, said primary abutment means and said latch element having relatively interlockable portions for securing said latch element against movement from said operative to said releasedposition thereof as long as either of said control elements is in its said primary limit position, and said secondary abutment means being cooperable with said latch element to move the latter from said operative to said released position thereof upon adjustment of both of said control members to their saidsecondary limit positions and upon subsequent movement of either of said control members beyond its said secondary limit position.

11. A dual control mechanism comprising a support, a pair of control levers pivotally mounted on said support and each being adjustable independently of the other within a predetermined idling range and beyond said range to an operative position, a pair of cam members connected, respectively, with said control levers and each having a circumferential cam surface and a notched portion providing an undercut recess at said cam surface, a latch element movably mounted on said support, and means resiliently urging said latch element into engagement with said cam surfaces, said latch element having foot portions adapted to enter said recesses, respectively, to determine primary and secondary limit positions of said control levers Within said idling range, and said foot pieces being interlockable with said recesses, respectively, upon adjustment of said control members into said primary limit positions thereof.

12. A dual control mechanism comprising a support, a pair of control levers pivotally mounted on said support and each being adjustable inde- 21 pendently of the other within a predetermined idling range and beyond said range to an operative position, a pair of cam members connected,

respectively, with said control levers and each having a circumferential cam surface and a notched portion providing a recess at said cam surface, a pair of rigidly connected foot pieces pivotally mounted on said support and adapted to enter said recesses, respectively, to determine primary and'secondary limit positions of said control levers within said idling range. and means resiliently urging said foot pieces into engagement with said cam surfaces, said foot pieces having toeportions and said recesses having undercut portions interlockable with said toe portions,

respectively, upon adjustment of said control levers to said primary limit positions thereof, and said foot pieces having heel portions cooperable REFERENCES CIT-ED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,596,513 Ainsworth Aug. 17, 1926 1,768,845 Thomas et a1 July 1, 1930 2,197,248

Bonham et al. Apr. 16, 1940 

